SAN JOSE, Calif. (AP) The San Jose Sharks have been at their best this postseason when they had little margin for error.

That's probably why they feel comfortable heading home for Game 5 of the Western Conference final against the Blues after a lackluster start led to a Game 4 loss in St. Louis.

Having squandered a series lead for the second time in this matchup, the Sharks know a loss Sunday could mean they won't get to play on home ice again this postseason.

"It's a great spot to be in," coach Peter DeBoer said Saturday. "This is supposed to be hard. What happened with Boston on the other side, that usually doesn't happen. Usually these are all six, seven hard-fought games, hard-fought series. We're right where I expected we would be, in a good spot going home, and we've got to get the job done."

After alternating wins in the first four games, the Sharks and Blues now have a best-of-three to decide who plays the Bruins in the Stanley Cup Final. Boston swept Carolina in the East and will have 10 days off before the start of the next round May 27.

Nothing has come easy for San Jose or St. Louis. The Blues went six games in the opening round against Winnipeg before needing double overtime in Game 7 of the second round against Dallas to make the conference final.

The Sharks, meanwhile, have endured two seven-game series - Vegas and Colorado. That's happened in part because they have appeared to let up when leading a series before responding with greater desperation.

San Jose is 0-6 this postseason when leading a series. But it is 10-2 when tied or trailing, including four wins in elimination games sparked by a comeback from 3-1 down in the opening round to the Golden Knights.

"There's a lot of emotion in the playoffs," Sharks captain Joe Pavelski said. "We're in the conference finals. We've had overtime wins, we've had game sevens. We've had emotional games for sure. You just lace them back up next game and you compete."

The Blues got a goal from Ivan Barbashev 35 seconds into Game 4 and added another late in the first period before hanging on for the 2-1 win Friday.

It was an impressive rebound from a crushing Game 3 loss when the Blues allowed the tying goal with 1:01 left in regulation and then the winner in overtime after the officials failed to see a hand pass by San Jose that set up Erik Karlsson's goal.

"We're in a good spot," coach Craig Berube said. "So just pushing and keep fighting and be aggressive. Just be aggressive as a team and be confident as a team. That's our message. You're going to have ups and downs in the playoffs and you have to move on from it. You really do. As much as we had to move on from that Game 3 loss we have to move on from last night's win."

The Sharks need to come out in Game 5 with the kind of play they showed in the final two periods Friday. They controlled the puck and hemmed the Blues into the defensive end for long stretches.

The only problem was St. Louis rookie goalie Jordan Binnington, who stopped all 11 shots in the second period and then nine of 10 in the third. He allowed only a power-play goal to Tomas Hertl on the way to his franchise-record 10th win this postseason.

Another big concern for the Sharks is the health of Karlsson, who played only one shift in the final 9:24 after an apparent injury. Karlsson missed 27 of the final 33 games in the regular season with groin injuries that have hampered him in the playoffs.

He's had big moments, with 14 assists and two goals, including the disputed overtime winner in Game 3 against the Blues. But he also seems to labor at times, as he did in the third period before taking an extended break when the Sharks were fighting for the tying goal.

He returned for the final 1:55 game with the goalie pulled but mostly stayed positioned at the point for passes and shots, his skating limited. DeBoer offered no update Saturday on Karlsson's condition.

The Blues will again be without defenseman Vince Dunn, who took a puck to the face in Game 3.

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AP freelancer Joe Harris in St. Louis, Missouri, contributed to this report